A known artificial disc is disclosed in U.S. Pat. Nos. 6,001,130. U.S. Pat. No. 6,001,130 discloses an artificial disc having a resilient core. Concaval-convex plates at least partly surround the resilient core to retain the core between adjacent vertebral bodies in a spinal column. The concaval-convex plates do not have any openings extending through the plates into which the core deflects.